I purchased a 4 X 5 Super D a couple of years ago and I must confess that I have not used it yet. I just noticed that the lensboard does not stay firm in its position on the lower side of the front standard. The upper side is spring load...this works fine. When the lensboard is inserted and the spring depressed, the lens board will slide back OK on the lower half but there is NOTHING to catch it other than the pressure from the spring pressing downward on the board. What's missing? Thanks.